1. Field of the Invention
The present invention generally relates to a technology for backing up and restoring data.
2. Description of the Related Art
A technology for recovering from a failure occurred in a storage device that constitutes an autonomous-distributed storage system has been disclosed. The autonomous-distributed storage system autonomously searches a location to read or write data without using an integrated management server. For example, a technology for recovering from a system failure such as data access failure in an autonomous-distributed storage system is disclosed in, for example, “Implementation of the Fat-Btree on nCUBE3”, Ryutaro Hiratsuka, et al., [online], [searched on Sep. 13, 2006], Internet URL: http://yokota-www.cs.titech.ac.jp/˜yokota/papers, dews99-2.PDF. The autonomous-distributed storage system has a directory structure (see FIG. 11) in which a route directory is shared by disks (i.e., disks 1 to 4), while other directories are distributed and held by the respective disks to enable an effective data search.
More specifically, as shown in FIG. 12, if a failure occurs in a storage device 2, a backup directory for the storage device 2 that is stored in a storage device 3 is added to a primary directory of the storage device 3, and a new primary directory is created. A backup directory corresponding to the newly created primary directory of the storage device 3 is stored in a storage device 4, and a backup directory corresponding to a primary directory of a storage device 1 is stored in the storage device 3. Thus, a primary directory of the storage device 2 is restored and data access is enabled.
However, in the conventional technology, if the system is disabled due to a failure, it takes time for the system to be recovered. In other words, the recovery process of the primary directory shown in FIG. 12 requires an amount of time equivalent to that taken to perform a process of actually adding data to the primary directory. Therefore, if a failure such as a storage-device failure occurs in the system, the system requires a considerable amount of time to recover from the disabled state and allow data access.